The Dow is inching towards an all-time high, on a boost from retailers Home Depot and Nike, while record daily US COVID-19 infections kept gains in check amid low liquidity in the final week of the year.
Home Depot and Nike Inc advanced one per cent and two per cent, respectively, against the backdrop of recent reports suggesting holiday sales were strong for US retailers.
Some early studies pointing to a reduced risk of hospitalisation in Omicron cases have helped investors look past the travel disruptions and powered the S&P 500 to record highs this week.
"The market thinks that Omicron is going to hit just a few sectors of the whole economy, and most stocks will be good for that," said Luiz Pacheco, wealth adviser at Brainvest Wealth Management based in Miami.
Meanwhile, the S&P 1500 airlines index shed 1.3 per cent. Delta Air Lines and Alaska Air Group canceled hundreds of flights again on Tuesday as daily tally of infections in the United States surged.
Six of the 11 major S&P sector indexes advanced. The energy index, though, slipped 0.6 per cent as oil prices slipped on demand concerns.
Typically, the final five trading days of the year and the first two of the subsequent year are seasonally strong for US stocks.
However, market participants warned against reading too much into daily moves as the holiday season tends to record some of the lowest volume turnovers that cause exaggerated price action.
In early trading on Wednesday, the Dow Jones Industrial Average was up 93.90 points, or 0.26 per cent, at 36,492.11, the S&P 500 was up 5.79 points, or 0.12 per cent, at 4,792.14, and the Nasdaq Composite was down 27.45 points, or 0.17 per cent, at 15,754.27.
The S&P 500 dipped on Tuesday in the lowest trading volume session of 2021, snapping a four-day winning streak.
As 2021 draws to a close, the main US stock indexes are on pace for their third straight year of stunning annual returns, boosted by historic fiscal and monetary stimulus.
The S&P 500 is looking at its strongest three-year performance since 1999.
The focus next year will shift to the US Federal Reserve's path of interest rate hikes amid a surge in prices caused by supply chain bottlenecks and a strong economic rebound.
Among other stocks, Rivian Automotive dropped 3.6 per cent after company announced it would delay deliveries of its electric pickup truck and sports utility vehicle with big battery packs to 2023.
Electric-car maker Tesla's CEO Elon Musk exercised all of his options expiring next year, signaling an end to his stock sales. Its shares dropped 1.3 per cent but were still on course to end about 54 per cent for the year.
Declining issues outnumbered advancers for a 1.16-to-1 ratio on the NYSE and for a 1.97-to-1 ratio on the Nasdaq.
The S&P index recorded 53 new 52-week highs and no new low, while the Nasdaq recorded 38 new highs and 240 new lows.